What are the limitations of Blender for Mac?
The feature support should be the same as any other system. The official MacOSX releases will be built using the available third party libraries which includes the newer features using opensubdiv, openvdb and alembic.
As with other platforms, cuda support is better than opencl. This will depend on what mac you have as newer macs now have AMD and Intel video cards. While technically a hardware issue, the hardware is tied to MacOSX. For Cycles rendering this could lead to render farms being more popular for mac users.
anyway newer macOS users should consider that blender DOES NOT SUPPORT METAL and since Apple is discontinuing OpenCL, reading this statement on blender official website can make you sad when it comes to use GPU rendering specially in cycles render engine:

GPU rendering is only supported on Windows and Linux; macOS is
currently not supported.

... and because of some technical issues (some of these issues mentioned here) it's hard to say that they are going to support Metal (at least soon)